1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device. More specifically, the present invention relates to a method of manufacturing a semiconductor device utilizing an energy beam, for example, such as a laser beam.
2. Description of the Prior Art
A solar cell or a linear optical sensor array are known as a semiconductor device using a semiconductor film as a photoactive layer. The present invention is directed to a method of manufacturing a semiconductor device having a plurality of photoelectric converting regions.
FIG. 1 is a cross-sectional view showing a fundamental structure of a prior solar cell. Such fundamental structure is disclosed, for example, in U.S. Pat. No. 4,281,208 assigned to the same assignee as the present invention. Here, the structure of solar cell shown in FIG. 1 will be described briefly within a limit necessary to understand the present invention.
A plurality of photoelectric converting regions 14a, 14b, 14c, - - - are formed on a glass substrate 10, transparent film electrodes 11a, 11b, 11c, - - - are formed corresponding respectively to these photoelectric converting regions at predetermined intervals. On each transparent film electrode 11a, 11b, 11c, - - - semiconductor film portions 12a, 12b, 11c, - - - constituted by an amorphous silicon are formed superposedly. Back film electrodes 13a, 13b, 13c, - - - extending as far as the adjacent transparent film electrodes and connected thereat are formed on semiconductor film portions 12a, 12b, 12c, - - - . Each semiconductor film portion 12a, 12b, 12c, - - - includes a PIN junction parallel to respective film surface and when light is incident through the glass substrate 10 and transparent film electrodes 11a, 11b, 11c, - - - photovoltaic forces are generated at respective semiconductor film portions 12a, 12b, 12c, - - - by the PIN junctions thereof. The photovoltaic forces generated by respective semiconductor film portions 12a, 12b, 12c, - - - are added arithmetically in series via the back film electrodes 13a, 13b, 13c, - - - connections to the adjacent transparent film electrodes.
For manufacturing the solar cell having such a structure a photoetching technique having super-high working precision is used. When using the photoetching technique, the process may be described with reference to the example in FIG. 1 as shown the transparent electrode film is first formed entirely on one main surface of the glass substrate 10, and photoresist film portions are formed on the areas corresponding to transparent film electrodes 11a, 11b, 11c. Next, etching is performed and the photoresist film portions are removed, for forming transparent film electrodes 11a, 11b, 11c. Thereafter, the semiconductor film is formed on the main surface of the glass substrate 10. The semiconductor film portions 12a, 12b, 12c, are formed by first forming photoresist film portions on the areas corresponding to the semiconductor film portions 12a, 12b, 12c, and thereafter etching. Although such photoetching is superb in the precise processing, it is susceptible to the defects on the semiconductor film due to pinholes in the photoresist film or peeling in a periphery of the photoresist film.
The above manufacturing without using the photoetching technique, can be accomplished using a laser beam as disclosed, for example, in U.S. Pat. No. 4,292,092 issued on Sept. 29, 1981. The method of irradiating via the laser beam is very effective in that precise processing can be performed without using the wet process at all.
However, according to the conventional method of irradiating via the laser beam, the following problems are still to be solved. When using the laser beam, the semiconductor film is divided into each photoelectric converting region by irradiating the laser beam to the adjacent spacing potion 12' of the photoelectric converting region in FIG. 2 and removing the semiconductor film in that portion, or the back electrode film is divided into each photoelectric converting region by irradiating the laser beam to the adjacent spacing portion 13' in FIG. 3 and removing the back electrode film thereof.
However, since the fused residues 12r or 13r of the semiconductor film or the back electrode film remain in the adjacent spacing portions 12' or 13', an accurate patterning can not be accomplished. Such residues 12r or 13r tend to remain in the both sides of the scanning axis of the laser beam. This is caused by the fact that, since the distribution of the energy density of the laser beam is slightly in the normal distribution, the energies in both side ends of the adjacent spacing portions 12' and 13' are smaller than that in the center thereof. Thus, the residues 12r or 13r in the adjacent spacing portions 12' or 13' to be removed, cause various problems. When the residue 12r of the semiconductor film remains in the adjacent spacing portion 12' in FIG. 2, after being divided into the semiconductor film in each respective region, the bonding strength of the back electrode film formed thereupon tends to reduce, ultimately resulting in a separation defect of the back electrode film. Then, when the residue 13r of the back electrode film material remains in the adjacent spacing portion 13' in FIG. 3, a short circuit defect may occur due to the direct contact of the transparent electrode film and the back electrode film in the same photoelectric converting region (cell).
Moreover, in order to connect the adjacent photoelectric converting regions 14a, 14b, 14c, - - - in series, for example, a portion of the transparent film electrode 11b having a length D exposed from the semiconductor film portion 12b on the right in FIG. 2, must be elongated to the greatest extent possible without reducing the effective area relative to the photoelectric converting region. In order to satisfy such a requirement, a prior art practice has been to reduce the scanning speed or to increase the scanning times of the laser beam. However, this decreases productivity and increases cost.